Hi Jim,
I do not know what kind of housing you are putting your PCB in, but from your 
outline description I am guessing some cast housing. You are also not giving 
us a clue about your application. You are also talking about punching instead 
of routing, so i am guessing CEM-3 instead of FR-4 as the PCB material.
In that case, your routing tolerances are your least problem; much more 
worrisome are likely the different thermal expansions of the PCB and the housing as 
well as swelling of the CEM-3 with moisture absorption.
GM ran into this with their windshield wiper controls: single-sided CEM-3 
PCBs in some combination of routing and housing tolerances requiring 
press-fitting the PCBs. The result: windshield wiper failures for some of the more 
high-end [read: high-powered=running hotter] SUVs within as little as 1 year after 
sale due to solder joint failures caused by PCB warping—over 4 million vehicles 
were ordered by NHSTA to be recalled. 

Werner

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------